Astarotte no Omocha!

In the medieval fantasy world of Alfheimr, succubus princess Astarotte Ygvar, the first princess of the kingdom of Ygvar, has just reached the age of 10. For the coming years of a young succubus' life, it is necessary for them to have a male harem. The princess, however, bears a great dislike against men, and only agrees to create a harem if a human male is to join. The catch is, nobody has been able to travel between Alfheimr and the human world, Midgard, for over a millennium.
from Manga Updates (edited)